The idea of united Europe started to become reality after World War II. In 1951, Germany, France, Italy, Belgium, Luxembourg, and the Netherlands signed the Treaty of Paris, which created the European Coal and Steel Community. The idea was to unite French and German capacities for production of these raw materials, essential for warfare. In 1957, six countries signed the Treaty of Rome, which created the European Economic Community. They also signed another pact creating the European Atomic Energy Community. Since 1993 the Copenhagen criteria determine the preconditions for membership. Besides the ability to cope with the obligations of membership and the economic criteria, the highest priority often goes to the political requirement of democracy, the rule of law, respect for human rights and protection of minorities. Formed as a club of six members, The European Union is a community of 28 countries which have gradually entered the European Union through five rounds of enlargement. The largest expansion occurred 2004 when 10 countries joined the European Union. The Republic of Croatia has a specific path towards the European Union. From independence until the signing the Accession Treaty Croatia was faced with various challenges that have impacted on the outcome of its integration time. Speaking about the future of the European Union, the new candidate member countries are Republic of Albania, Republic of Montenegro, The Former Yugoslav Republic of Macedonia, Republic of Turkey and Republic of Serbia. The potential candidate members are Bosnia and Herzegovina and Kosovo.